PHP XML validation fails on valid XML - php

Question

I use the following function to validate XML coming from a Web API before trying to parse it:
function isValidXML($xml) {
$doc = #simplexml_load_string($xml);
if ($doc) {
return true;
} else {
return false;
}
}
For some reason, it fails on the following XML. While it's a bit light in content, it looks valid to me.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><connection-response-list xmlns="http://www.ca.com/spectrum/restful/schema/response" />
Why would this fail? I tried another method of validate the XML that used DOMDocument and libxml_get_errors(), but it was actually more fickle.
EDIT: I should mention that I'm using PHP 5.3.8.

Answer 1

I think your interpretation is just wrong here – var_dump($doc) should give you
object(SimpleXMLElement)#1 (0) {
}
– but since it is an “empty” SimpleXMLElement, if($doc) considers it to be false-y due to PHP’s loose type comparison rules.
You should be using
if ($doc !== false)
here – a type-safe comparison.
(Had simplexml_load_string actually failed, it would have returned false – but it didn’t, see var_dump output I have shown above, that was tested with exactly the XML string you’ve given.)

Answer 2

SimpleXML wants some kind of "root" element. A self-closing tag at the root won't cut it.
See the following code when a root element is added:
<?php
function isValidXML($xml)
{
$doc = #simplexml_load_string($xml);
if ($doc) {
return true;
} else {
return false;
}
}
var_dump(isValidXML('<?xml version="1.0" encoding="UTF-8" standalone="yes"?><root><connection-response-list xmlns="http://www.ca.com/spectrum/restful/schema/response" /></root>'));
// returns true
print_r(isValidXML('<?xml version="1.0" encoding="UTF-8" standalone="yes"?><root><connection-response-list xmlns="http://www.ca.com/spectrum/restful/schema/response" /></root>'));
// returns 1
?>
Hope that helps.